JPH11258186A - Method and apparatus for measurement of stress by x-rays - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stress measuring method whose resolution is high in the depth direction of a sample and in which the large penetration depth of X-rays is obtained and to obtain its apparatus. SOLUTION: In a stress measuring method and an apparatus 1 which executes the method, diffracted X-rays D from the inside of a sample S are detected by a concentration method, and a stress inside the sample S is measured. In this case, X-rays B from an X-ray source 11 are condensed on a focus circle C which is situated along a plane crossing the surface of the sample S and which passes the center position S0 of a measuring place inside the sample S. The sample S is irradiated with the X-rays B which are passed through their condensed place F. An R-ray detector 13 which is provided with a monochromator is scanned near the diffraction angle θ of the sample S with reference to the irradiated X-rays B. The diffracted X-rays of a crysal on the focus circle C which passes the center position S0 of the measuring place are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a stress in a sample by detecting diffracted X-rays by a concentrated method.

[0002]

2. Description of the Related Art An X-ray stress measurement method is widely known as a method for non-destructively evaluating the surface stress of a polycrystalline substance, for example, a metal, and measures a diffraction angle at which a diffraction X-ray intensity shows a peak. This is a method of calculating stress from the diffraction angle. A concentrated method generally known as one of the diffraction X-ray detection methods may be applied to such an X-ray stress measurement method.

The diffraction angle θ determined by the crystal lattice spacing is
It is detected by the positional relationship between the X-ray source, the X-ray detector and the sample. In the focusing method, as shown in FIG. 2, an X-ray source and an X-ray source are arranged on a circle C ₁ (focal circle) in contact with the surface of a sample to be measured.
A configuration is adopted in which the line detector and the diffraction surface are positioned (this is called a concentration condition) and arranged so that the oblique incidence angle of X-rays and the detection angle of diffraction X-rays are equal (both are θ). Thereby, the diffraction X-ray measurement target surface (the sample surface in this arrangement)
Will be concentrated at the position of the X-ray detector. Therefore, steep diffraction X
It is characterized in that a line intensity profile is obtained, whereby the diffraction angle can be measured with high resolution. As shown in FIG. 3, in order to obtain the intensity profile of the diffracted X-ray, for example, the sample is rotated around the point S ₀ as the rotation center (rotation angle ± Δθ; FIG. 3 shows a state rotated by Δθ). , In conjunction with this, the X-ray detector is set to the point S _0.
Is rotated on the goniometer circle C ′ with the rotation center as the rotation center (FIG. 3 shows a state in which the sample is rotated by 2Δθ corresponding to the rotation of the sample by Δθ). As a result, the diffracted X-ray having the diffraction angle θ + Δθ concentrates on the X-ray detector. Therefore, the intensity profile of the diffracted X-ray can be obtained by variously changing the values of θ and Δθ.

[0004]

However, the above-mentioned focusing method usually employs a configuration in which an X-ray source having a fixed width (about 100 μm) is arranged on a focal circle, or a diffraction method on a focal circle in front of the X-ray source. Since a slit for narrowing the X-ray peak width (however, it is necessary to have a width capable of securing a predetermined X-ray intensity) is provided, the width of the emitted X-ray and the spread of the irradiation area on the sample surface are reduced. Basically, X that does not originally satisfy the concentration condition
Lines are also detected. Therefore, the intensity of the diffracted X-ray at a position shifted from the position that completely satisfies the concentration condition slowly decreases. That is, the geometric allowance δ shown in FIG. 4 (for example, the shift amount of the sample surface at which the diffracted X-ray intensity becomes の of the peak value) δ increases. This means that even if the surface of the sample to be measured is displaced by ± δ in the radial direction of the focal circle from a position that completely satisfies the concentration condition, diffracted X-rays from the surface enter the X-ray detector. Means Therefore, unless consideration is given to the depth of penetration into the sample described later, the diffraction X-ray intensity measured with the sample surface positioned on the focal circle is all from the region extending from the sample surface to the depth direction δ. Diffraction X
The intensity of the line. Usually, the emission width of the X-ray source is about 100 μm. In this case, δ is considered to be about several 100 μm, although it depends on the crystal state of the sample. On the other hand, the actual penetration depth of the X-ray into the sample (diffraction X
The depth at which a line can be obtained is at most several tens of μm. Therefore, in the stress measurement by the concentrated method in which a normal X-ray source is arranged, several tens μm
Only diffracted X-rays having average information of the crystal state in the extent region can be measured. For example, a detailed analysis of the deterioration mechanism of a sample requires obtaining a high measurement resolution in the depth direction of the sample, but the conventional lumped method could not sufficiently respond to this.

When a normal X-ray source is used, as described above, the penetration depth of X-rays into a sample is at most several tens of μm.
m, especially several micrometers or less when the sample is a metal, so that only the average stress of the extreme surface layer of the sample can be measured. Therefore, there is also a problem that accurate internal stress cannot be measured in detailed analysis of a deterioration mechanism of a plating material or various structural materials, for example, analysis of a stress crack generated on a circuit of a semiconductor device.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems in the prior art, and has a method and an apparatus for measuring stress which have a high measurement resolution in the sample depth direction and can obtain a large X-ray penetration depth. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a method for measuring a stress in a sample by detecting diffracted X-rays from the inside of the sample by a concentrated method. X-rays from an X-ray source are condensed on a focal circle along a plane and passing through a center position of a measurement point in the sample, and the sample is irradiated with the X-rays after passing through the light-condensing point, and A stress measurement method is provided, wherein an X-ray detector provided with a monochromator is scanned near a diffraction angle of a sample to detect a diffraction X-ray of a crystal on a focal circle passing through the center of the measurement point.

According to this invention, the width of the X-rays condensed on the focal circle is smaller than the emission width of the X-ray source in the conventional focusing method. It becomes smaller according to. This means that the measurement resolution in the sample depth direction increases, and if the position of the sample is slightly moved in the depth direction, it is possible to detect a diffraction peak from a specific position in the sample in the depth direction. Become.

Preferably, the X-ray source is a synchrotron radiation source.

According to this invention, since the intensity of the synchrotron radiation light source is strong and the parallelism is good, the penetration depth of the X-ray into the sample increases, and the X-ray focusing optical system allows the X-ray to be focused on the focal circle. Since the light is condensed to a very small width, the resolution in the sample depth direction is dramatically improved.

Further, the present invention provides an apparatus capable of suitably implementing the above method.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view schematically showing one embodiment of a stress measuring device according to the present invention.

As shown in FIG. 1, a stress measuring device 1 according to the present invention includes an X-ray source 11, an X-ray focusing optical system 12, an X-ray detector 13, and a sample moving device 14, and a sample moving device 14.
Is irradiated with X-rays B on a sample S attached to the sample, and diffracted X-rays D satisfying a concentration condition are detected. The X-ray source 11 in the present embodiment includes a spectroscopic system for monochromaticizing synchrotron radiation, and is a synchrotron radiation light source (for convenience, capable of emitting X-rays with high intensity and excellent parallelism).
1 (represented by small dimensions). The synchrotron radiation light source can emit continuous X-rays having a high intensity, and an appropriate X-ray according to the crystal system of the sample S is selected using the above-described spectral system for monochromatization. As the X-ray source, other than a synchrotron radiation light source, a source capable of irradiating the sample S with monochromatic X-rays having high intensity and good parallelism can be suitably used. X-ray B emitted from X-ray source 11
Is an X-ray condensing optical system 1 so as to focus on a point F on a focal circle C.
2 collects light. In the present embodiment, the X-ray focusing optical system 12 employs an oblique incidence reflection system and has an elliptical reflection surface. However, the reflection surface may be a hyperboloid or a combination of a hyperboloid and an ellipsoid.

The X-rays B once condensed pass through the slit 121 provided at the point F, and then diffuse again according to the convergence angle.
A predetermined area of the sample S is irradiated. Here, the sample S is
The position is adjusted by the sample moving device 14 so that the point S0 at the depth d from the surface to be measured (the center position of the measurement point) coincides with the point C0 on the focal circle C. By using the X-ray source 11 as a synchrotron radiation light source having high intensity and good parallelism as described above, a sufficient penetration depth can be obtained. Converge,
By adjusting the position of the sample S, it is possible to detect a diffracted X-ray from a specific depth inside the sample S.

The diffracted X-ray D from the sample S passes through a slit 131 provided at a point G on the focal circle and is detected by an X-ray detector 13 having a monochromator (not shown) in front. The monochromator has a detection wavelength band corresponding to the wavelength of the X-ray irradiated on the sample. Further, the monochromator includes an arc-shaped reflecting optical system having a focal point at point G,
For example, scattered X-rays or diffraction X-rays from the sample surface shown in FIG.
The line D ′ is suppressed from entering the X-ray detector 13 body.
The slit 131 and the X-ray detector 13 are mounted on a goniometer (not shown) having the point C0 as the center of rotation.
The sample S and the sample moving device 14, and the X-ray detector 13 and the slit 131 can be arbitrarily rotated about the point C0 as a center of rotation, and the intensity profile of the diffracted X-ray can be measured. The stress in the sample S can be calculated from the diffraction angle obtained from the intensity profile. Therefore, for example, the internal stress of a metal material such as a plating material can be measured at each predetermined depth, and a detailed analysis of the material deterioration mechanism becomes possible.

[0016]

As described above, according to the present invention, since the X-ray from the X-ray source is condensed on the focal circle passing through the center of the measurement point in the sample, the X-ray source has a certain width. The measurement resolution in the sample depth direction can be obtained to the extent that it cannot be obtained by the conventional intensive method due to having. Therefore, the stress can be measured at a certain depth of the sample, and the detailed analysis of the deterioration mechanism of the semiconductor device and various structures can be performed.

Further, if the X-ray source is an X-ray source having a high intensity and a good parallelism as represented by a synchrotron radiation light source, for example, a high resolution in the sample depth direction can be obtained, and Strong intensity can be obtained even with diffracted X-rays from a deeper position. Therefore, even if the sample is a plating material or the like, it is possible to precisely measure the internal stress, which is not limited to the extreme surface layer, and it is very effective for detailed analysis of the degradation mechanism of the plating material and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing one embodiment of a stress measuring device according to the present invention.

FIG. 2 is a sectional view schematically showing a conventional device.

FIG. 3 is a conceptual diagram of a method for measuring an intensity profile of a diffracted X-ray by the apparatus shown in FIG.

FIG. 4 is a diagram showing a change in diffraction X-ray intensity due to a deviation from a concentration condition of a sample surface.

FIG. 5 is a diagram showing scattered X-rays or diffracted X-rays from the sample surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stress measuring device 11 X-ray source 12 X-ray focusing optical system 13 X-ray detector 14 Sample moving device 121 Slit 131 Slit B Irradiation X-ray D Diffracted X-ray D 'Scattered X-ray C Focus circle C' Goniometer circle S Sample

Claims (4)

[Claims] 1. A method for measuring a stress in a sample by detecting diffracted X-rays from inside the sample by a convergence method, wherein a focal circle passes along a plane crossing the surface of the sample and passes through a center position of a measurement point in the sample. An X-ray detector that focuses X-rays from an X-ray source, irradiates the sample with the X-rays after passing through the focus, and includes a monochromator near the diffraction angle of the sample with respect to the irradiated X-rays And detecting a diffraction X-ray of a crystal on a focal circle passing through the center position of the measurement point. 2. The method according to claim 1, wherein the X-ray source is a synchrotron radiation source. 3. An apparatus for measuring a stress in a sample by detecting a diffracted X-ray from inside the sample by a concentration method, comprising: an X-ray source; a center of a measurement point in the sample along a plane crossing the surface of the sample. An X-ray condensing optical system for condensing X-rays from the X-ray source on a focal circle passing through the position, and scanning is performed near a diffraction angle of the sample with respect to X-rays irradiated on the sample after passing through the condensing point A stress measurement device comprising: an X-ray detector having a monochromator; and a sample moving device for moving the sample in a radial direction of the focal circle. 4. The stress measuring device according to claim 3, wherein the X-ray source is a synchrotron radiation light source.